Triple balloon catheter

ABSTRACT

The present invention advantageously provides a method and system for cryogenically ablating large areas of tissue within the left atrium. In an exemplary embodiment a cryotherapy device includes a catheter body, a proximal end and a distal end; a first lumen; a second lumen; and an ablation element expandable from a first diameter to a second diameter, the ablation element having a surface portion that conforms to the uneven surface topography of the cardiac tissue. The ablation element can include one or more deformable balloon and/or flexible elements. The surface of the balloon can further be shaped by regulation of pressure within the one or more balloons. In an exemplary method, a tissue ablation device is provided and tissue in the left atrium is ablated with the device, whereby the ablation is created by freezing tissue.

CROSS-REFERENCE TO RELATED APPLICATION

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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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FIELD OF THE INVENTION

The present invention relates to a method and system for interventionalelectrophysiology and minimally invasive cardiovascular treatment.

BACKGROUND OF THE INVENTION

Minimally invasive surgical techniques are known for performing medicalprocedures within all parts of the cardio-vascular system. Exemplaryknown procedures include the steps of passing a small diameter,highly-flexible catheter through one or more blood vessels and into theheart. When positioned as desired, additional features of the catheterare used, in conjunction with associated equipment, to perform all or aportion of a medical treatment, such as vessel occlusion, tissue biopsy,or tissue ablation, among others. Almost always, these procedures areperformed while the heart is beating and blood is flowing. Notsurprisingly, even though visualization and positioning aids areadequate for general placement of the device, maintaining the device ina selected position and orientation can be difficult as the tissue movesand blood flows, especially during a procedure that must be donequickly. As diagnostic and visualization equipment and techniques havecontinued to evolve, it has become possible to identify tissue areas tobe treated with greater precision than the ability to quickly situatethe device and effectuate treatment.

In addition to the challenges presented by moving tissue and flowingblood, the actual topography of the tissue being treated presentschallenges. For example, unlike stylized drawings that depict theinterior of the chambers of the heart as having smooth, evenly curvedwalls leading neatly to tubular blood vessels, the interior surfaces ofthe heart's chambers are irregular, uneven, and fibrous, as are theopenings to blood vessels. Thus, for procedures that call for uniformtissue contact or tissue contact along an extended line, the structureand techniques for use of known devices can be deficient in someregards.

Even if a device is capable of being properly placed and held inposition at the proper orientation; and even if the device is suitablefor the tissue topography at the treatment site, the device can benevertheless not fully suitable to achieve the desired outcome. By wayof example, catheter-based devices are known for placement in the leftatrium for ablating tissue within the atrium for the purpose ofelectrically isolating one or more pulmonary veins from the atrium in anattempt to increase the success rate of atrial fibrillation ablation.

In one type of prior art device disclosed in U.S. Patent Publication2002/012836 A1, and as shown in FIG. 1 (prior art), a sheath or guidecatheter 10 is inserted into a blood vessel 12 that leads to the rightatrium 14 of the heart 16 and passed through an opening created in theseptum 18 that separates the right and left atria into the left atrium20. As shown in FIG. 2 (prior art), a treatment element 22 is passedthrough the guide catheter 10, deployed from an opening in the distalend thereof, and caused to form a substantially circular loop that istraverse or perpendicular to the longitudinal axis of the guide catheter10. A distal tip element 24 that extends distally beyond the circularloop is inserted into a pulmonary vein 26 as a guide and placement aidfor the loop. As shown in FIG. 3 (prior art), the treatment element 22in the form of a loop is placed so that it encircles the opening orentry of the pulmonary vein 26, known as the ostium, and tissue isablated by microwave heating of the contacted tissue. The intendedresult is a substantially uniform circle of ablated tissue 28 as shownin FIG. 4 (prior art). Also as shown in FIG. 4 (prior art), such adevice can be used in an attempt to create linear lesions 30 and 32 aswell.

In practice, uniform, unbroken lesion lines are hard to create with suchloop shaped ablation elements. Also, with respect to both the circularand the linear lesions formed by microwave ablation, it should be notedthat the lesion formed is relatively narrow and has a width thatcorresponds to about the width of the catheter. Devices that use a laserto ablate tissue provide a similar result; namely, a very narrow lesion.Further, because a laser ablates a very narrow line of tissue, precisealignment of the device is very important. However, for the reasons setforth above, such precision is very difficult to achieve.

Catheter-based devices have been introduced that cryogenically ablatetissue. These devices are structurally very different from RF catheterbased devices, and they are not similar or comparable variations on thesame theme. Not only are the structures that encompass the respectiveablation technologies different, but so are the devices for controllingthe ablation process, evaluating the progress and extent of ablation,and ensuring patient safety.

For example, to create a large “ring” with an RF catheter it istypically necessary to make a series of adjoining spot lesions ofrelatively small size using small electrodes if one wishes to minimizeRF output. This is significant because use of a large electrode and/orhigh power output can seriously injure tissue at other than the intendedtreatment site. This is especially important with respect to creatinglesions in the pulmonary veins because the veins are juxtaposed withbronchial tubes and other sensitive pulmonary tissue within which it ishighly undesirable to create ancillary lesions. By contrast, cryogenicablation of tissues does not need to be accomplished “bit by bit” forfear of energy transmission into the affected tissue as the transfer ofheat occurs at the medical device.

Nevertheless, given the uneven topography of the tissue, anatomicaldifferences between patients, and the tortuous environment of the bloodflowing through the vasculature mentioned above, secure placement of acryogenic device against a pulmonary vein remains challenging. Moreover,if too much force is applied to the device and thus the tissue, risk ofdamaging the pulmonary vein increases—e.g., the vein could be deformed,ruptured, stenosed, or otherwise injured. In view of the above, it wouldbe desirable to provide a medical device and treatment methods of usethereof that allow for secure placement against uneven, topographicalsurfaces such as those found in the left atrium of the heart whilereducing or otherwise minimizing the risk of unwanted injury to thetissue region being treated.

SUMMARY OF THE INVENTION

The present invention advantageously provides a method and system forcryogenically ablating large areas of tissue within the left atrium. Inparticular, the present invention advantageously provides a medicaldevice and treatment methods of use thereof that allow for secureplacement against uneven, topographical surfaces such as those found inthe left atrium of the heart while reducing or otherwise minimizing therisk of unwanted injury to the tissue region being treated.

In an exemplary embodiment a cryotherapy device is provided formodifying the electrophysiological properties of cardiac tissue havingan uneven surface topography, wherein the device includes a catheterbody having a substantially fixed diameter, a proximal end and a distalend; a first lumen for permitting passage of a cooling fluid from theproximal end to the distal end; a second lumen permitting return of thecooling fluid from the distal end to the proximal end; and an ablationelement expandable from a first diameter that is substantially the sameas the diameter of the catheter body to a second diameter that is atleast twice the diameter of the catheter body, the ablation elementhaving a surface portion that conforms to the uneven surface topographyof the cardiac tissue. The ablation element can include one or moreballoons and/or a flexible element that is deformed by moving the distalend of the catheter toward the proximal end of the catheter. The surfaceof the balloon can further be shaped by regulation of pressure withinthe one or more balloons.

The invention also includes a method for modifying theelectrophysiological properties of cardiac tissue wherein a tissueablation device is provided and tissue in the antrum of the left atriumis ablated with the device. In an exemplary method, only tissue in theantrum is ablated, and the ablation is created by freezing tissue. Inaddition, an exemplary method of a cryomaze procedure is provided whichcan be performed without the need to arrest the heart of the patient.

A cryogenic device is also provided, including a first substantiallynon-compliant balloon; a second substantially compliant balloonpositioned distal to the first balloon; and a third substantiallycompliant balloon surrounding the first and second balloons. The firstballoon may be constructed from PET, nylon or similar polymericmaterials or composites, and the second balloon may be constructed frompolyurethane, latex, or similar polymeric materials or composites. Thefirst balloon may have an elastic modulus between approximately 2700 MPaand approximately 4250 MPa, while the second balloon may have an elasticmodulus between approximately 50 MPa and approximately 600 MPa. Thefirst and second balloons may be expandable independently of oneanother, and may not be in fluid communication with each other. Thedevice may also include a cryogenic fluid supply in fluid communicationwith the first balloon, and a non-cryogenic fluid in fluid communicationwith the second balloon. Further, an interstitial region may be definedbetween the third balloon and at least one of the first and secondballoons; and a vacuum source can be placed in fluid communication withthe interstitial region.

A medical system is also provided, having a flexible catheter body; afirst balloon disposed on the catheter body; a second balloon disposeddistally of the first balloon, wherein the second balloon is morereadily deformable than the first balloon; and a third balloonsubstantially enclosing the first and second balloons to the define aninterstitial region therebetween.

A method for treating cardiac tissue is also provided, includingpositioning a medical device proximate an ostium such that a firstballoon of the medical device abuts cardiac tissue proximate to theostium and at least a portion of a second balloon located distal to thefirst balloon is positioned within the ostium, where the first andsecond balloons are substantially enveloped within a third balloon;expanding the second balloon to substantially occlude the ostium; andablating cardiac tissue with at least one of the first and secondballoons. Expanding the second balloon may include partially inflatingthe second balloon to substantially less than its maximum volume ordiameter. The first balloon may define an elastic modulus at least fivetimes greater than an elastic modulus defined by the second balloon.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 depicts a prior art technique for placing a distal portion of amedical device within the heart;

FIG. 2 illustrates a prior art technique for positioning a prior artdevice within the left atrium;

FIG. 3 depicts a prior art technique for creating a lesion with a priorart microwave ablation device;

FIG. 4 shows lesions formed using the prior art techniques and devicesof FIGS. 1, 2 and 3;

FIG. 5 is a schematic illustration of a cryogenic ablation system inaccordance with the present invention;

FIG. 6 is a side view of an exemplary ablation element for the system ofFIG. 5;

FIG. 7 depicts the ablation element of FIG. 6 is an expanded state;

FIG. 8 shows an alternative embodiment of the ablation element of FIG.6, wherein a membrane is disposed over expansion elements positioned inan expanded state;

FIG. 9 is a front view of the ablation element of FIG. 6, wherein anablation pattern created by the device is shown;

FIG. 10 illustrates an alternative embodiment for the ablation elementin a partially expanded state;

FIG. 11 illustrates the ablation element of FIG. 10 in a fully expandedstate;

FIG. 12 depicts the ablation element of FIG. 10 in a partially inflatedstate suitable for deflection;

FIG. 13 depicts the ablation element of FIG. 10 in the partiallyinflated state shown in

FIG. 12 being deflected to a curved configuration;

FIG. 14 a shows yet another embodiment of the ablation element;

FIGS. 14 b-16 illustrate the ablation element in exemplary deploymentconfigurations;

FIG. 17 a shows yet another embodiment of the ablation element;

FIG. 17 b shows an exemplary use of the ablation element of FIG. 17 a;

FIG. 18 illustrates yet another embodiment of an ablation element;

FIG. 19 shows the ablation element of FIG. 18 in a deflected condition;

FIG. 20 show yet another ablation element in accordance with theinvention; and

FIG. 21 illustrates an ablation device in accordance with the inventionwithin the left atrium of the heart having created lesions in the leftantral region

FIG. 22 illustrates a method of use of the present invention;

FIG. 23 illustrates an alternative method of use of the presentinvention;

FIG. 24 illustrates another method of use of the present invention; and

FIG. 25 illustrates an additional method of use of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

With respect to the treatment of atrial fibrillation, it is believedthat the creation of a conduction block or an interruption of theelectrical signal flow path from the region of the atrium and thepulmonary vein is an effective treatment for atrial fibrillation.Further, while it is believed that the creation of a narrow annularlesion at or very near the ostium of the pulmonary vein is an effectiveway to create a conduction block, notwithstanding the difficulty ofmaking such a lesion, it is believed that creating one or morenon-annular lesions in different locations is not only more readilyaccomplished with reliability, but it is more clinically effective.

In view of the preceding, the present invention provides apparatus andmethods for modifying the electrophysiological properties of large areasof tissue rather than narrow, annular lesions at locations that are notconfined solely to the ostium, although ablation of tissue near theostium and/or in the atrial wall may be included. More particularly, thepresent invention provides devices that are suitable to cryogenicallyablate regions of tissue in the antrum region of the left atrium inaddition to other atrial tissue that may be deemed to be arrhythmogenic.The antrum is the area between the mouth or ostium of a pulmonary veinand the atrium. The antrum of each pulmonary vein is not identical insize or shape and the tissue topography renders it very difficult oralmost impossible to create a ring of tissue. Accordingly, the presentmethod calls for ablating large regions of tissue in the antrum torender the tissue electrically dysfunctional.

Referring now to FIG. 5, an exemplary system is depicted that issuitable for performing cryogenic antral ablation. The system generallyincludes a medical device, which may include an elongate, highlyflexible ablation catheter 34 that is suitable for passage through thevasculature. The ablation catheter 34 includes a catheter body 36 havinga distal end 37 with an ablation element 38 at or proximal to the distalend. The distal end 37 and the ablation element 38 are shown magnifiedand are described in greater detail below. The ablation catheter 34 hasa proximal end 40 that is mated to a handle 42 that can include anelement such as a lever 44 or knob for manipulating the catheter body 36and the ablation element 38. In the exemplary embodiment, a pull wire 46having a proximal end and a distal end has its distal end is anchored tothe catheter at or near the distal end 37. The proximal end of the pullwire is anchored to an element such as a cam 48 in communication withand responsive to the lever 44. The handle 42 can further includecircuitry 50 for identification and/or use in controlling of theablation catheter or another component of the system.

Continuing to refer to FIG. 5, the handle 42 can also include connectorsthat are matable directly to a cryogenic fluid supply/exhaust andcontrol unit or indirectly by way of one or more umbilicals. In thesystem illustrated, the handle 42 is provided with a first connector 54that is matable with a co-axial fluid umbilical (not shown) and a secondconnector 56 that is matable with an electrical umbilical (not shown)that can further include an accessory box (not shown). In the exemplarysystem the fluid supply and exhaust, as well as various controlmechanisms for the system are housed in a single console 52. In additionto providing an exhaust function for the ablation catheter fluid supply,the console can also recover and/or recirculate the cooling fluid. Thehandle 42 is provided with a fitting 58 for receiving a guide wire (notshown) that is passed into a guide wire lumen 60.

Still referring to FIG. 5, the ablation element 38 is shown as a doubleballoon, wherein an inner balloon 62 is contained by an outer balloon64. A coolant supply tube 66 in fluid communication with the coolantsupply in the console 52 is provided to release coolant from one or moreopenings in the tube within the inner balloon 62 in response to consolecommands and other control input. A vacuum pump in the console 52creates a low pressure environment in one or more lumens within thecatheter body 36 so that coolant is drawn into the lumen(s), away fromthe inner balloon, and toward the proximal end of the catheter body. Thevacuum pump is also in fluid communication with the interface of theinner and the outer balloons so that any fluid that leaks from the innerballoon is contained and aspirated. Still referring to FIG. 5, thehandle includes one or more pressure sensors 68 to monitor the fluidpressure within one or both of the balloons, blood detection devices 70and pressure relief valves 72. When coolant is released into the innerballoon 62, the inner and the outer balloon 64 expand to a predeterminedshape to present an ablation surface, wherein the temperature of theablation surface is determined by the material properties of thespecific coolant selected for use, such as nitrous oxide, along with thepressure within the inner balloon and the coolant flow rate.

Although the double balloon type ablation element 38 illustrated in FIG.5 can be an effective ablation tool, FIGS. 6-20 illustrate otherconfigurations for the ablation element that are capable of creatingwide-area ablation patterns. For example, as shown in FIG. 6, a distalcatheter portion 74 includes longitudinal elements 76 secured to a maincatheter body 78 proximally, and to a tip element 80, distally. A pullwire 82 or pushrod connected to a manipulation element 44 at theproximal end of the catheter and to the tip element 80 is movablelongitudinally to move the tip element longitudinally. Electrodes 84 canbe associated with one or more of the longitudinal elements for use inmonitoring or evaluating electrical activity in tissue.

As shown in FIG. 7, the pull wire 82 has been pulled proximally to drawthe tip element 80 toward the catheter body 78. This causes thelongitudinal elements 76 to deform and bend or bow radially outward. Inone embodiment, each of the longitudinal elements 76 are provided withcoolant injection tubes 83 disposed within a lumen defined by eachlongitudinal element, wherein coolant is recovered in the lumen which isin fluid communication with a low pressure source. Thus, each of thelongitudinal elements 76 are cooled. Although the injection tubes 83 canall be supplied with coolant simultaneously, if desired, less than allof the injection tubes can be supplied with coolant to provideselectively radial cooling.

As shown in FIG. 8, the longitudinal elements can support a single or adouble layer flexible member 85 that envelops them. Instead of, or inaddition to coolant being circulated through the longitudinal members asdiscussed with respect to FIG. 7, coolant can be circulated through thechamber defined by the elements and the flexible member as describedwith respect to FIG. 5 and the pull wire 82 can be used to deform theballoon by moving the distal end of the device proximally and distally.

FIG. 9 is a front view of the device of FIGS. 7 and 8 and it illustratesthe general shape of the periphery 86 of a lesion formed by cryoablationusing the exemplary device in the expanded state. By contrast, spot orlinear lesions can be created when the distal catheter portion 74 is inthe non-expanded state illustrated in FIG. 6.

Referring now to FIG. 10, a catheter is provided with an ablationelement 88 similar to the double balloon structure of FIG. 5 so that adistal tip region 90 is radially expandable to at least double thediameter of a catheter body 92 over a 2cm to 3cm length. The ablationelement 88 is provided with a cryogenic fluid injection tube 94 havingone or more fluid outlets 96 along its length in the distal tip region.Coolant is withdrawn though an outer lumen 98 at reduced pressure. Apull wire 100 or pushrod is used to deflect the distal catheter portionas shown in FIG. 11 so that a large, distal facing surface 102 can beplaced into contact with tissue. Although the balloon when inflated asshown in FIG. 10 has a substantially greater radius than the catheterbody 92, when the pull wire 100 is used to draw the distal tip towardthe catheter body as shown in FIG. 11, the balloon expands even furtherand presents a flattened tip that is suitable to blot large areas oftissue.

Referring now to FIG. 12, an ablation element 104 is provided with adistal portion 106 that is inflatable, one or more coolant injectionorifices 108 and an exhaust lumen 110. Referring to FIG. 13, theablation element 104 is shown with a pull wire 111 or pushrod connectedto a manipulation element at the proximal end of the catheter and thetip element 12 so as to be movable longitudinally to deflect the tipelement off axis. In addition to providing a relatively long and wideablation surface, the ablation element can be provided with a notch 114to accommodate or fit over a ridge of tissue.

FIGS. 14 a-16 illustrate an embodiment for an ablation element, whereinfirst and second balloons, 116 and 118, respectively, are enveloped by athird balloon 120. The first and the second balloons 116 and 118 are influid communication with inflation and exhaust lumens as describedabove, wherein the third balloon 120 is only in communication with avacuum or low pressure source. Each of the first and second balloons maybe provided with a predetermined or substantially preformed shape ordimension and/or may be pressurized or otherwise inflated to provide anoverall surface topography for the ablation element. Additional shapingmay be provided by manipulation of a pull wire 119 as described above orby regulation of the pressure in the exhaust flow path.

FIG. 17 a provides an additional illustration of a triple-balloonconfiguration of the catheter 34 for the medical system. In particular,a first balloon 150 may be disposed on the elongate body of the catheter34. The first balloon 150 may be substantially non-compliant when in aninflated state. For example, the first balloon 150 may be constructedfrom polyethylene terephthalate (“PET”), nylon or similar polymericmaterials or composites. Located distally of the first balloon 150 onthe catheter 34 may be a substantially compliant, second balloon 152.The second balloon 152 may be constructed from polyurethane, latex, orsimilar polymeric materials or composites. The substantially increasedelasticity or compliance of the second balloon 152 as compared to thefirst balloon 150 may result in the second balloon 152 being morereadily deformable than the first balloon 150 when inflated and/or incontact with a targeted tissue area. To facilitate the desiredconformity or lack thereof, the first balloon may have an elasticmodulus approximately five to fifty times that of the second balloon.For example, the first balloon may define an elastic modulus betweenapproximately 2700 MPa and approximately 4250 MPa, while the secondballoon may have an elastic modulus between approximately 50 MPa andapproximately 600 MPa

The first and second balloons 150, 152 may be inflatable and/orotherwise operable independently from one another. For example, theinterior of the first balloon 150 may be in fluid communication with afirst inflation lumen 154 and a first exhaust lumen 156. These inflationand exhaust lumens may be in fluid communication with a fluid sourceand/or vacuum source, respectively, contained within the console 52. Theinterior of the second balloon 152 may be in fluid communication with asecond inflation lumen 158 and a second exhaust lumen 160. The separatefluid flow paths of the first and second balloons enable them to besealed or otherwise not in fluid communication with each other. Theseinflation and exhaust lumens may also be in fluid communication with afluid source and/or vacuum source, respectively, contained within theconsole 52. Of note, the first and second balloons may be in fluidcommunication with independent, separated first and second fluid sources162 a, 162 b respectively, (shown in FIG. 5). The first fluid source 162a may contain a cryogenic coolant or refrigerant, while the second fluidsource 162 b may contain a non-cryogenic fluid, such as saline,non-cooled gas, or the like.

The catheter 34 shown in FIG. 17 a may further include a third balloon164 surrounding, substantially enclosing or otherwise enveloping thefirst and second balloons. The third balloon 164 may be substantiallycompliant and be constructed from polyurethane, latex, or similarpolymeric materials or composites, having a modulus of elasticity orflexibility substantially larger than that of the first balloon. Thethird balloon 164 may be disposed about the first and second balloons todefine an interstitial region 166 therebetween, which may be in fluidcommunication with an interstitial lumen 168. The interstitial lumen 168may be in fluid communication with a vacuum source in the console 52,and which may be the same or additional to the vacuum source(s) in fluidcommunication with either of the first and second exhaust lumens 156,160.

Now referring to FIG. 17 b, an exemplary method of use of the deviceshown in FIG. 17 a is illustrated. In particular, the catheter 34 may bepositioned and subsequently operated to thermally treat a targetedtissue area, such as an ostium 170 of a pulmonary vein in the atrium ofthe heart. For example, the catheter 34 may be delivered to or otherwisepositioned within an atrium of a heart intravascularly or otherwise asdescribed herein. The catheter 34 may be positioned such that at least aportion of the second balloon 152 is disposed within a pulmonary vein orother vascular conduit. The second balloon 152 may then be expanded orotherwise inflated to substantially occlude the pulmonary vein or othervessel in which it resides. The expansion of the second balloon 152 maybe achieved by delivering a fluid, such as a non-cryogenic fluid,saline, or the like, from the second fluid source 162 b through thesecond inflation lumen 154 and into the interior of the balloon 152.Further, as there may be variations in the size, shape or otherdimensions of the vessel being occluded, the second balloon 152 may beselectively, controllably expanded to a fraction of its overallinflation/size capacity to obtain the resulting, desired occlusion. Thispartial inflation may be facilitated by monitoring the pressure withinthe second balloon and terminating inflation upon reaching a desired orpredetermined pressure threshold value or range. Another example ofproviding a controlled, fractional inflation of the second balloon mayinclude delivering a predetermined volume of inflation medium to thesecond balloon 152 to reach a predetermined or preselected inflationsize (whether volume, outer circumference, diameter, or the like). Inaddition to the selective inflation dimensions of the second balloon152, occlusion may further be facilitated by the complaint nature of thesecond balloon 152, described above. Having a sufficiently-compliantinterface with the contacting tissue allows the second balloon 152 toconform to the uneven surface topography of the occluded vessel,resulting in an enhanced, more effective occlusion.

Anchoring and/or sufficiently occluding the targeted vessel with thesecond balloon 152 further allows positioning the first balloon 150 toabut against a tissue wall or region (such as the atrial wall)surrounding or otherwise extending from the ostium. The first balloon150 may then be operated to exchange thermal, ablative energy betweenthe balloon 150 and the proximate tissue. In particular, a cryogeniccoolant or medium may be circulated through the first balloon 150 viathe first inflation and exhaust lumens, 154, 165.

Of course, during the positioning and operation of the first and secondballoons, the third balloon 164 surrounds the first and second balloons,thereby providing both a safety barrier in the event of a structuralfailure of either the first and second balloons, as well as aconformable interface pliably extending between the first and secondballoons. The third balloon 164 thus further facilitate occlusion of theostium, as well as contact with the surrounding tissue wall proximatethe first balloon 150. During operation, the interstitial region may bekept under vacuum to minimize any space between the third balloon 164and the first and second balloons to reduce thermal isolation andthereby increase heat transfer, as well as providing for the removal ofany fluid leaking into the interstitial region 166.

Referring now to FIGS. 18 and 19, yet another configuration for anablation element is shown wherein an ablation element includes anelastically deformable, thermally-transmissive tip element 122 securedto the distal portion of a catheter body 124. When a load is applied tothe tip element 122 it deforms. For example, FIG. 19 illustrates the tipelement subject to an axial load, such as is encountered when the tip ispressed against tissue. As shown, the distal portion of the tip element122 presents a wider ablation surface when deflected as compared to thenon deflected state. When the load is removed from the tip, it returnsto the shape illustrated in FIG. 18. Fluid supply and exhaust lumens areprovided as disclosed above. Also as described above, a pull wire 125can be secured to the tip element 122 to help deform the element so thatit doesn't need to be pressed hard against tissue. In an exemplaryembodiment the tip element 122 is configured so that it is biased intothe shape illustrated in FIG. 18. Proximal tension is applied to thepull wire 125 to deform or aid in deforming the tip element to anexpanded configuration as shown in FIG. 19. When proximally directedtension is reduced on the pull wire 125, the biasing force of the tipelement causes it to return to the configuration shown in FIG. 18.

FIG. 20 illustrates yet another configuration of an ablation elementwherein a catheter body 126 has a distal end 128 covered with a mass ofthermally conductive, highly elastic material, such as a cohesive gel130. When the distal end 128 and the gel 130 are pressed against tissue,the gel deforms to provide an enlarged distal end portion as shown bythe dashed line 132. Coolant exiting a coolant supply tube 134 cools thedistal end 128 and the gel 130.

Turning now to FIG. 21, an exemplary procedure is illustrated wherein anablation element 136 in accordance with the invention has been deliveredtranseptally into the left atrium. In the illustration, the ablationelement 136 is a balloon that is partially inflated with a nitrous oxidecoolant so that it has a “squishy” or highly compliant character anddimensioned so that it can “blot” or contact an area of tissueapproximately 28 to 30 mm in diameter. In the exemplary procedure, theballoon is inflated to the desired degree of firmness, or lack thereof,before being advanced toward tissue and the balloon's surface is chilledto a temperature in the range of minus 30 degrees Centigrade to minus 80degrees Centigrade. The balloon is then placed into contact with tissuein the antrum 138 and the tissue is ablated. The balloon is moved to oneor more additional areas of the antrum 138 until the desired tissuemodification has been achieved. The balloon can be placed so as tocreate individual distinct lesions or overlapping lesions. In thisfashion, large contiguous lesions can be created. The pattern 139 shownin FIG. 21 illustrates an exemplary lesion periphery created with theablation element 136.

Because the doctor is not attempting to create a “ring,” the balloondoes not have to be centered on the ostium 140 and no anchoring isneeded. In general, for any of the disclosed cryoablation devices,precise alignment is not as important as with respect to other devices.This is significant, because the precise positioning within the antrumis difficult to achieve. The balloon does not enter the pulmonary vein142. However, depending upon placement of the balloon, the temperatureachieved, and the duration that the balloon is left in place, ispossible to ablate tissue in the ostium 140 in addition to tissue withinthe pulmonary vein 142, as well as the antrum 138.

In another exemplary method, the ablation catheter 34 as described abovemay be used to create a series of lesions in the heart, whereby theablation catheter is maneuvered into the left atrium of the heart fortreatment of an arrhythmia or other cardiac abnormality. Primarily, theablation catheter may be positioned in proximity to the heart using oneof either a subxyphoid approach, a thoracotomy approach, or a sternotomymethod. Each of these methods provides surgical access to the heart forsubsequent positioning and insertion into the left atrium of a medicaldevice for ablation of the desired tissue.

Now referring to FIG. 22, employing a subxyphoid technique, the heart200 may initially be accessed through a puncture technique using thesame 17-Gauge Tuohy needle that is used to enter the epidural space whenadministering epidural anesthesia (typically .about.100 mm overalllength, and 1.5 mm O.D.). A subxyphoid incision 202, which is typicallyless than 10 centimeters in length, is created. As the needle approachesthe heart 200 under fluoroscopic guidance, small amounts of contrastmedia are injected to document penetration of the needle tip as itprogresses towards the heart. Once properly positioned as indicated bythe assistance of medical imaging, a guide wire may be passed throughthe needle. As a result, a standard introducer sheath, and subsequentlyan ablation catheter 34, may be passed into a position in proximity tothe heart 200.

Now referring to FIGS. 23 and 24, a thoracotomy technique may also beperformed for providing initial access the heart 200, whereby one ormore small thoracotomy incisions 204 are made in the chest wall betweenthe ribs to permit access for thoracoscopic instruments and cameras,which provide dissection and visualization capabilities in thepericardial space for insertion and manipulation of medical instruments,including the ablation catheter. The small thoracotomy incisions aretypically less than 10 centimeters in length. In this approach, thedecompression of the pleural space may be necessary in order to achievepericardial access.

As shown in FIG. 25, a third approach employs a sternotomy, which iscommonly performed for open heart surgery, and is the leastminimally-invasive of the approaches described above. A full sternotomymay include multiple incisions and the eventual division of the sternum,thereby providing direct access to the heart 200.

Upon generally accessing the heart through any of the above-mentionedapproaches, the ablation catheter must further enter the internalchambers of the heart for the eventual ablation of the desired tissue.Such internal access may be achieved by directing the ablation catheterthrough one of the pulmonary veins or the aorta, through the hearttissue or left atrial appendage, or through the superior vena cava andthe septum wall.

To access the internal chambers of the heart through either of thepulmonary veins or the aorta, a pursestring suture may be placed in anyof the pulmonary veins or the aorta. Using a seldinger technique, anintroducer may be inserted through the pulmonary veins or aorta, andinto the left atrium. Once the introducer is appropriately positioned,the ablation catheter may be guided through the introducer and into theleft atrium for subsequent ablation of the desired tissue.

Access to the internal chambers of the heart may further be accomplisheddirectly through an exterior surface of the heart, or through the leftatrial appendage. For example, a pursestring suture may be placed in theleft atrial appendage, through which an introducer and/or guidewire ispositioned. As such, the ablation catheter may be guided directly intothe left atrium through the left atrial appendage or other exteriorheart surface for subsequent ablation of the desired tissue within theheart.

The internal chambers of the heart may additionally be accessed by atransseptal approach. A transseptal approach may include placing apursestring suture in the lateral wall of the right atrium, providingaccess for a needle to further be inserted into the heart. The needle,as well as a guidewire and introducer, may be initially guided into theright atrium through the superior vena cava. Further, the needle may bemaneuvered through the atrial septum and into the left atrium, at whichpoint the guide wire may be inserted to dilate the opening in the atrialseptum. Upon sufficient dilation of the septum, the introducer may bedirected through the septum and into the left atrium. Subsequently, theablation catheter may be guided through the introducer and into the leftatrium for ablation of the desired tissue.

Upon accessing the internal chambers of the heart, and moreparticularly, the left atrium, the ablation catheter can be positionedin the orifice of the right inferior pulmonary vein, possibly employingthe aid of fluoroscopy or other medical imaging to facilitate accurateplacement of the device. Positioning and occlusion of the vein orificemay further be confirmed through the administration of a contrast dye.Once in the desired location, the ablation catheter can be used tocreate a lesion around the orifice of the right inferior pulmonary vein.The ablation catheter may then be repositioned in the right superiorvein, the left superior vein, and the left inferior pulmonary vein forthe creation of additional ablative lesions about the orifices of therespective vessels. An additional lesion may be created to connect thelesions of the left-sided pulmonary veins with the lesions of theright-sided pulmonary veins, to form somewhat of an “eyeglass” pattern.

Upon completion of the creation of the pulmonary vein lesions, one ormore lesions, either spot lesions or linear in nature, extending fromthe left inferior pulmonary vein to the mitral valve annulus can becreated using the ablation catheter. In order to confirm that theablative lesions have in fact been successfully created, a pacingcatheter or other electrical-sensing device can be used to monitorelectrical pulses in the affected tissue, and ablation may bereinstituted in the desired locations, if necessary. Once the desiredportions of the heart have been ablated, the introducer sheath and theablation catheter can be removed, and the surgical openings may beappropriately closed.

While ablation procedures are typically performed on an arrested heart,the procedure described above may be performed with the ablationcatheter on a beating heart employing a thoracoscopic or smallthoracotomy approach, which reduces the recovery time for a patient aswell as reducing the complexity of the surgical procedure. As such, thehigher-risk portions of a typical maze procedure, namely a sternotomy,cardiopulmonary bypass, and/or aortic cross-clamping or cardiac arrest,are no longer necessary.

The ablation catheter used to create the lesions described above mayinclude any of the features previously discussed. Moreover, in order toease the use of the catheter in the transseptal approach, the length ofa portion of the catheter may be reduced from that of a standardcatheter inserted into the femoral artery or other insertion pointdistant from the heart. Furthermore, the flexibility of the portions ofthe catheter may be altered in order to provide increased malleabilityin order to facilitate the accurate positioning of the ablation elementwithin the heart. Alternatively, pull-wires or other deflectionmechanisms can be integrated with or otherwise coupled with the catheterfor steering and/or positioning, as is known in the art.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed herein above. In addition, unless mention was made above tothe contrary, it should be noted that all of the accompanying drawingsare not to scale. A variety of modifications and variations are possiblein light of the above teachings without departing from the scope andspirit of the invention, which is limited only by the following claims.

What is claimed is:
 1. A method for treating cardiac tissue, comprising: positioning a medical device having a longitudinal axis proximate an ostium such that an expanded first balloon of the medical device abuts cardiac tissue proximate to the ostium and at least a portion of an unexpanded second balloon located distal to the first balloon is positioned within the ostium, wherein the first and second balloons are substantially enveloped within a third balloon; expanding the second balloon to substantially occlude the ostium; and ablating cardiac tissue with at least one of the first and second balloons.
 2. The method of claim 1, wherein expanding the second balloon includes partially inflating the second balloon to less than half of its maximum diameter.
 3. The method of claim 1, wherein the first balloon has an elastic modulus that is at least five times greater than an elastic modulus of the second balloon.
 4. The method of claim 1, wherein the first balloon has an elastic modulus between approximately 2700 MPa and approximately 4250 MPa.
 5. The method of claim 4, wherein the second balloon has an elastic modulus between approximately 50 MPa and approximately 600 MPa.
 6. The method of claim 1, wherein the first balloon has an anterior face that lies in a plane that is at least substantially orthogonal to the longitudinal axis of the medical device.
 7. The method of claim 6, wherein the third balloon is sufficiently compliant to conform to at least a portion of the anterior face of the first balloon to enhance thermal transfer from the anterior face of the first balloon to the third balloon.
 8. The method of claim 6, wherein the second balloon has an anterior face and a posterior face.
 9. The method of claim 8, wherein at least a portion of the anterior face of the first balloon is in contact with at least a portion of the posterior face of the second balloon when the first and second balloons are expanded.
 10. The method of claim 1, wherein ablating cardiac tissue includes delivering a cryogenic coolant to the first balloon.
 11. The method of claim 6, wherein expanding the second balloon includes delivering a non-cryogenic fluid to the second balloon.
 12. The method of claim 1, wherein an interstitial region is defined between the third balloon and at least one of the first and second balloons, further comprising drawing a vacuum on the interstitial region.
 13. The method of claim 1, wherein the first balloon is constructed from polyethylene terephthalate or nylon.
 14. The method of claim 13, wherein the second balloon is constructed from polyurethane or latex.
 15. The method of claim 11, wherein the first balloon and the second balloon are expandable independently of each other.
 16. The method of claim 15, wherein the first balloon and the second balloon are not in fluid communication with each other.
 17. A method for treating cardiac tissue, the method comprising: positioning a medical device having a longitudinal axis proximate an ostium such that an expanded first balloon of the medical device abuts cardiac tissue proximate to the ostium and at least a portion of an unexpanded second balloon located distal to the first balloon is positioned within the ostium, wherein the first and second balloons are substantially enveloped within a third balloon, the first balloon defining an anterior face that lies in a plane that is at least substantially orthogonal to the longitudinal axis of the cryogenic device; expanding the second balloon to substantially occlude the ostium; and ablating cardiac tissue with at least one of the first and second balloons.
 18. The method of claim 17, wherein the second balloon defines an anterior face and a posterior face, at least a portion of the anterior face of the first balloon being in contact with at least a portion of the posterior face of the second balloon when the first balloon and the second balloon are expanded.
 19. The method of claim 17, wherein the third balloon is sufficiently compliant to conform to at least a portion of the anterior face of the first balloon to enhance thermal transfer from the anterior face of the first balloon to the third balloon.
 20. A method for treating cardiac tissue, the method comprising: positioning a medical device having a longitudinal axis proximate an ostium such that an expanded first balloon of the medical device abuts cardiac tissue proximate to the ostium and at least a portion of an unexpanded second balloon located distal to the first balloon is positioned within the ostium, wherein the first and second balloons are substantially enveloped within a third balloon, the first balloon defining a posterior face and an anterior face that lies in a plane that is at least substantially orthogonal to the longitudinal axis of the cryogenic device, the second balloon defining a posterior face and an anterior face; expanding the second balloon to substantially occlude the ostium, at least a portion of the anterior face of the first balloon being in contact with at least a portion of the posterior face of the second balloon when the first balloon and the second balloon are expanded; and ablating cardiac tissue with at least one of the first and second balloons, the third balloon being sufficiently compliant to conform to at least a portion of the anterior face of the first balloon to enhance thermal transfer from the anterior face of the first balloon to the third balloon. 